The U.S.S. Enterprise arrives to pick up research personnel on the second planet of the star Minara. While Kirk, Spock and McCoy are on the surface, they are captured by the Vians and find themselves in an underground chamber with a mute humanoid, who McCoy names "Gem." The Vians take Kirk as a test subject to torture. Gem, who turns out to be a fully functional empath, heals Kirk's wounds. The Vians explain that they are testing Gem's capacity for compassion and self-sacrifice to see if her people are worthy as a species to be saved from their doomed sun.

James Doohan (Lt. Cmdr. Montgomery Scott)
Kathryn Hays (Gem)
Alan Bergmann (Lal)
George Takei (Lt. Hikaru Sulu)
Davis Roberts (Dr. Ozaba)
Jason Wingreen (Dr. Linke)
Willard Sage (Thann)